The present invention relates generally to an improved solar energy collector, and more particularly to a solar heat concentrator which includes, in combination, a solar radiation concentrator means in the form of a line focus Fresnel array, and an absorber means cooperating with the array for receiving the concentrated solar energy. With the continuing utilization and ultimate partial depletion of available fossil fuels, alternate sources of energy have become desirable, provided feasible means and techniques can be found for their utilization. In this connection, solar energy may be employed as a high-grade power source for the generation of usable energy with this source of energy being freely available and non-polluting to the environment. Conversion of solar energy into usable energy may typically be achieved by thermodynamic arrangements, such as, for example, by the generation of steam or other heated fluid for ultimate utilization at a power conversion site. One approach which is commonly taken for conversion of solar energy is the utilization of flat absorbers to heat a fluid transfer medium such as water, the heated water then being transferred to either a thermally insulated reservoir or a zone wherein heat may be extracted. Such absorbers are normally referred to as "flat plate collectors." Since collector surface area must be substantial, the cost of such collectors along with the thermal efficiency at low ambient temperatures renders certain designs disadvantageous. These disadvantages are overcome with the structure and design of the present invention.
In conventional or known solar energy systems, such as flat plate collectors or the like, a number of common problems have existed and the existence of these problems has retarded the growth and acceptance of solar heating systems. Normally, the primary problem is the initial on-site installation cost, with this cost normally being large due to the excessive size of conventional systems. Furthermore, complex manifolding of the individual collectors in the system has presented problems due to leakage effects and the like. The weight of the installation has also presented problems, particularly the weight of a fluid-loaded system. When a roof mounted flat plate system is specified, particularly in an existing structure, the load bearing capability of the structure is frequently insufficient to support the fluid-loaded systems and structural supports must be provided. A further problem has existed with most flat plate solar heating elements, due to the low velocities normally utilized in the system. With low velocities, fluid corrosion and plugging of transmission lines may be more likely to occur than in systems employing high velocity transfer rates.
Conventional flat plate systems are normally cost-effective only if both heating and cooling may be achieved in a single installation, with a coefficient of performance being necessarily greater than about 0.6 in the cooling mode. With the existence of such a requirement, gaseous fluid cooling is not generally feasible.
In the present solar heat concentrator system, the design illustrated is one employing generally horizontally disposed cylindrical parabolas forming the array. It will be appreciated, of course, that generally vertically disposed cylindrical parabolas may be employed to form the line array, with the collector or absorber means being arranged generally accordingly, and with the elongated axis of the cylindrical parabolas being, of course, generally parallel to the elongated axis of the collector or absorber.
It has been predicted that the total electrical power demand for the United States of America in the year 1980 will be approximately 9.times. 10.sup.12 Kilowatt-hours. This power demand is substantially equivalent to that amount of incident solar radiation falling upon an area of only 1,531 square miles of land area located at approximately 33.degree. North Latitude in a given year. Such a latitude is substantially coincident with that of the State of Arizona. Assuming an efficiency of conversion of solar energy to electrical energy of only 15%, the area required to obtain the projected electrical power demand for the United States of America in the year 1980 is approximately 10,000 square miles, with the area reasonably being expected to provide at least a substantial portion of the projected electrical power demand for the United States of America for the calendar year 1980.
Solar energy is, of course, available for immediate conversion without further depletion or utilization of fossil fuels. The system of the present invention renders it possible to fabricate relatively modest solar energy conversion plants suitable for use in heating and cooling of residential dwellings, as well as commercial establishments with modest to moderate power requirements. This system efficiently and economically converts solar energy to other usable forms of energy at an amortized cost no greater than that cost required for fossil fuel conversion.
At those latitudes in which the United States of America is situated, sunlight is never available on a 24-hour per day basis, and at the same time, each day of the solar year provides a certain reasonable amount of potential sunlight. The sun is, nevertheless, available for exposure to the surface of the ground for a maximum of 50% of the total time of a given year within any given location. Depending upon climatic conditions, there will be a reduction from the 50% maximum occasioned by cloud cover, as well as a reduction due to the presence of natural or artificial obstacles. However, with the time available for exposure to the sun, it is, nevertheless, economically feasible to employ solar energy as the primary source of energy, with this primary source being supplemented by available fossil fuels. It will be appreciated that the utilization of fossil fuels may be required only during the night-time hours, or upon the occurrence of periods of heavy and extended cloud cover.